Abstract

Epoxy system having 10% by vol. of fly ash fillers with their surfaces covered by paraffin oil was made and the responses to exposure by immersion in waterat 75C in one case and water containing smaller amounts of dilute acid in theother were monitored. Weight recordings up to 100 h were noted regularly on thetest coupons exposed to the two media. The samples exposed to 100 h duration were later on subjected to compression test to evaluate the strength. In one case, a set of samples were immersed in water for a prolonged period of 1000 h before subjecting these also to compression tests.
The result showed increased absorption in acid bearing medium. The strength of the plain water exposed samples were lower than the dry counterparts. Samples that had an immersion in medium containing acid showed a further but marginaldrop in strength compared to the plain water case. However, the prolonged period plain water immersed sample exhibited considerable drop in strength. These are explained using scanning fractography where surface features of compression failed samples are recorded. The plain water as well as the acid media exposed ones show a plasticised matrix and in some places a cavity-like feature, left bythe separating ash particles, whose number showed a perceptible increase for the acid bearing system compared to the plain water case. Longer exposed samples showed the loss of fly ash due to the surface of the matrix holding them showing a step-like expanded appearance indicating the interfacial regions being affected by the prolonged exposure time. These and other features are discussed in this report.